1. character string The definition of ：

（1） Single character ：

char ch='i';// Definition of a single character 

（2） One dimensional string array ：

char arr[]="love";（ The one-dimensional string array defined by this method must be assigned )
char arr[4];（ If you want to create a memory application, you can store 3 An array space of characters ）
char arr[5]=”love”;（ open up 5 Bytes of space to store characters love, The last byte stores '\0' character ）
char arr[5]={'l','o',v','e'};( open up 5 Bytes of space to store characters love, The last byte stores '\0' character )

2. String length

（1）sizeof(arr) Is to find the number of characters in the string , because \0 It's also a character , So add one to the actual length of the array ;

（2）strlen（arr） because strlen meet \0 Will stop , So the result is the actual length of the array

3. The difference between string and character array ：

because C Not in the language string keyword , So you can't define a string , Only character arrays can be used to represent strings , Therefore, many people think that the two are the same concept , I used to think so , Later, I heard the teacher mention that there is a difference between string and character array , So I started flipping through some books , Just to understand The difference between the two , Next, please listen to me ：

（1） A character array ：

Is to define a character array , The space requested from memory is the number of elements in the array +1, Store the character elements of the array into memory

char arr1[] = { 'l','o','v','e' };

（2） character string ：

Is to define a character array , The space requested from memory is the number of elements in the array +1, Store the character elements of the array into memory +'\0', At compile time, the compiler will automatically add this value to the end of the string , A string is a Read only character array , You cannot change the internal data of the string through the pointer

char arr2[] = "love";

Simply put ：c The language string consists of C Add... At the end of the character array '\0' Deformed into .

#include<stdio.h>
int main(void)
{
	char arr1[] = { 'l','o','v','e' };
	char arr2[] = "love";
	printf("arr1 The length of  :%zu\n", sizeof(arr1));
	printf("arr2 The length of  :%zu\n", sizeof(arr2));
	printf("arr1 The length of  :%d\n", strlen(arr1));
	printf("arr2 The length of  :%d\n", strlen(arr2));
	printf("arr1 The content of  :%s\n",arr1);
	printf("arr2 The length of  :%s\n", arr2);
	return 0;
}

  notes ： The third line appears ：arr1 The length of :36 And the fifth line appears ：arr1 The content of :love Scald, scald, scald, scald love The reason is that strlen and printf All functions encounter '\0' Just stop , Because... Is not added when defining the character array '\0' Lead to '\0' Location unknown , So this happens , Use my previous blog （ First time to know C Language （1）） Make a picture for everyone to understand ：